Configless with Serverless

Configless is a Serverless plugin and library of TypeScript decorators that set the config for Lambda functions in serverless.yml and provide middleware for common tasks.

Install

yarn add configless

Example

@Service({
  environment: { tableName: 'users-table' },
})
export class UserService {
  @Env() tableName: string;

  @Endpoint('GET', '/users')
  @Handler()
  @Respond(200)
  async getUsers() {
    return getFromTable(this.tableName);
  }

  @Endpoint('POST', '/users')
  @Handler()
  @Respond(201)
  async createUser(@Body() userData: object) {
    const newUser = addToTable(this.tableName, userData);
    return newUser;
  }
}

Then add a functions.ts file:

export default addServices(exports, [
  UserService,
  OtherService,
]);

Add the plugin in serverless.yml, no functions config needed:

plugins:
  - configless/plugin

The above will produce the following configuration:

functions:
  getUsers:
    environment:
      tableName: users-table
    events:
    - http:
        method: GET
        path: "/users"
    handler: functions.service0_getUsers
  createUser:
    environment:
      tableName: users-table
    events:
    - http:
        method: POST
        path: "/users"
    handler: functions.service0_createUser

Available Decorators

Handler

@Handler({ ...functionConfig })
async someLambda(event, context) {}

Handler creates the config for the method and includes any passed config object. The name of the method is the name of the Serverless function.

Handler also wraps methods in an AWS.Lambda#invoke call.

@Handler()
async sendNotification(event) {}

@Handler()
async sendMessage(event) {
  // in production, instead of calling the actual method,
  // it will invoke the appropriate AWS Lambda function and pass the event data
  new NotificationService().sendNotification(data);
}

Service

@Serivce({ ...functionConfig })
class MyService {

}

Service will copy a passed config object to each of its Handler methods. The configs are deep merged together, with precedence given to the @Handler method's config.

Env

@Service()
class MyService {
  @Env() envProperty: string; // process.env.envProperty

  @Env('PROPERTY_NAME') localProperty: string; // process.env.PROPERTY_NAME
}

Class properties marked with @Env() will be set a value from process.env. If a string parameter is passed, it uses that as the environment variable key. Otherwise, it will use the name of the property.

Endpoint

@Endpoint('GET', '/users', { cors: true })
@Handler()
async getUsers() {}

Endpoint adds an http event to the function's events list. It must be passed an http method and a pathname. Any additional config can be passed as an object.

Respond

@Endpoint('GET', '/users', { cors: true })
@Handler()
@Respond(200, { Header: 'value' })
async getUsers() {
  return ['Bob', 'Kate', 'Giuseppe'];
}

Respond transforms the return result of the method by making the result a JSON string and adding a status code. A second headers object parameter is optional.

The above method returns this result:

{
  statusCode: 200,
  headers: { Header: 'value' },
  body: '["Bob","Kate","Giuseppe"]'
}

Body

Body is a parameter decorator that passes in the result of JSON.parse(event.body). If needed, event and context will still be passed to the method.

@Handler()
async method(@Body() body, event, context) {
  body === JSON.parse(event.body); // true
}